Wireless communications devices, such as cellular phones, often use a cellular network to route communications from an originating device to a target device within a communications system. Some wireless communications devices are able to directly communicate with each other without the use of a cellular network. Often, this direct communication is used for short-range ‘push-to-talk’ type communications.
In some wireless devices, direct communication between a pair of wireless communications devices requires the use of a frequency hopping communications protocol, such as MotoTalk™ by Motorola, Inc. of Schaumburg, Ill. MotoTalk™ is deployed in a 900 MHz ISM band (Industrial, Scientific and Medical) and employs frequency hopping (FH) wireless channelization. The FH spectral distributions are governed by the Federal Communications Commission (FCC) and must meet distribution requirements that minimize interference uniformly across the ISM band.
Communications sent between an originating device and a target device within a communications system require a communications protocol, such as such as MotoTalk™. There are three phases to each communication, including a “Connection Establishment” (CE) phase in which the communication is established, followed by a “Traffic” phase in which audio/visual/textual data is sent, and a “Super Stop” phase in which the communication is terminated using a super stop burst.
With reference to FIG. 2, when sending a communication between an originating device 210 and a target device 230, a repeating device is used 220 that simply amplifies a received communication 202 and retransmits the communication 202, is used. The repeating device 220 allows for communications between an originating device 210 and a target device 230 that are too far apart for direct communication. Typically, more than one repeating device 220 may be used in a communications system 200.
In order to support the repeating device 220 within the communications protocol, the durations of synchronization bursts 251, traffic channel bursts 261, and PID bursts 281 are all increased to 30 ms, and the duration of acknowledgement (ACK) bursts 291 sent back from the target device 230 are reduced to 15 ms. The repeating device 220 communicates with the originating device 210 on uplink frequencies and with the target device 230 on downlink frequencies. Additionally, if the communication system 200 has multiple repeaters 220, a repeater available sequence 300 is included in the CE phase 240 of the communication 202 in order to determine which repeater 220 is available for use to retransmit communication 202. Furthermore, a repeater request sequence 310 having a series of repeater request bursts 311 (i.e. RREQ1 312, RREQ2 314, and RREQ3 316) is added to the CE phase 240 to let the originating device 210 indicate to any available repeating device 220, which repeating device 220, if any, the communication 202 should proceed through. A series of repeater acknowledgement (RACK) bursts 331 may be sent by the repeating device 220 to the originating device 210 to acknowledge receipt of the repeater request sequence 310.
As a result, this leads to a total time of as much as 1435 mS or more to establish communication between the originating device 210 and the target device 230. Moreover, the repeating device 220 does not begin transmitting the communication 202 received from the originating device 210 to the target device 230 until an acknowledgement (ACK) burst 291 is transmitted to the originating device 210 from the repeating device 220, which is approximately 675 ms after the originating device 210 begins transmitting the communication 202 resulting in some delay between the time the communication 202 is transmitted by the originating device 210 and received by the target device 230. The acknowledgement burst 291 confirms that the target device 230 is within range of the repeating device 220 and that the target device 230 is ready to receive the transmission. The transmission of the acknowledgement burst 291 from the repeating device 220 to the originator 210 indicates that the repeating device 220 and the target device 230 are within range and available.
These transmissions and acknowledgments may substantially increase the amount of time between when the communication device is activated and when communication actually starts. As a result, it would be desirable to reduce the delay between the time the communication is transmitted by the originating device and received by the target device within a communications system employing a frequency hopping protocol.